The inventors developed a system adopting a combination of a magnetic pole array including a plurality of magnetic poles arranged in a straight line, and a coil array including a plurality of coils for detecting a position based on the magnetic pole array (e.g., Patent Publication 1: JP2009-276827A). In the system, the magnetic poles are arranged at the same pitch such that magnetic poles of N and S are arranged alternately, i.e., the adjacent magnetic poles have the opposite polarities N and S. The coil array detects a phase based on the magnetic pole. In this approach, pitch numbers of the magnetic poles in the magnetic pole array cannot be determined from the coil array. In this regard, the signal from the coil array changes cyclically for each of the magnetic poles. Therefore, using this information, the number of cycles in which the signal from the coil array changed is counted to determine the pitch numbers of the magnetic poles. However, in the method, in the case where data of the pitch numbers of the magnetic poles is lost due to an instantaneous power failure or the like, restarting operation becomes difficult.
Detection of the pitch numbers of the magnetic poles of the magnetic pole array and detection of the phase relative to the magnetic pole can be used, e.g., for controlling a linear motor, in addition to detecting a position of a moving vehicle. For example, a linear synchronous motor is used as the linear motor, the pitch numbers of the magnetic poles of the magnetic pole array and the phase relative to the magnetic pole are detected, and feedback control is provided for the linear motor. In both of the control of the linear motor and position detection of the moving vehicle, if the pitch numbers of the magnetic poles in the magnetic pole array are found without counting cycles of the signal, control can be implemented without any significant troubles.